The present invention relates to a bearing device for a horizontal shaft type rotating machine and, in particular, relates to a bearing device which feeds lubricant oil to a sliding bearing which supports a rotating shaft.
In a conventional self oil feeding type sliding bearing device which is applied to a horizontal shaft type rotating machine such as a horizontal shaft type electric motor, the lubricant oil was pumped up by making use of the rotating shaft and was fed on to the lubricating surface of the bearing and wherein ordinarily an oil ring or viscosity pump was disposed inside or near the bearing device and the lubricant oil was pumped up from an oil tank located at a lower part of the bearing device. In such instance, the lubricant oil which was fed to the bearing portion and had contributed to the lubrication of the bearing lubricating surface was heated due to shearing frictional action caused by the bearing surface and the heated lubricant oil dropped off from the both ends of the bearing and returned to the oil tank.
As indicated above, the lubricant oil which dropped off from the both ends of the bearing had been heated, it was necessary to reduce the temperature of the lubricant oil as much as possible by cooling in order to reuse the heated lubricant oil for circulation. However, the lubricant oil which has been used for lubrication is mostly mixed with air, and the lubricant oil in the oil tank which has been discharged from the bearing generates air bubbles and gradually clouds the oil into a milky color. When cooling such milky clouded and heated lubricant oil via heat radiation to the outside, the heat radiation efficiency is very low, because of the extreme reduction in the heat conductivity of the lubricant oil due to the air bubble inclusion therein. Further, when the lubricant oil of high temperature yet containing the air bubbles is directly fed onto the bearing lubricating surface, the cooling and lubricating effect of the lubricant oil for the bearing is lowered.
One of the countermeasures to the above problem is disclosed in German Patent No. 961584 in which the rotating shaft is supported by the bearing in the bearing box which stores lubricant oil in the bottom thereof, an oil ring is disposed inside the bearing box and the lubricant oil is pumped up and fed on to the bearing lubricating surface, and further in such construction the oil tank which is located at the bottom portion of the bearing box and stores the lubricant oil is divided into a plurality of oil chambers, and as well the respective oil chambers are communicated via respective communicating tubes provided at the respective bottoms of the oil chambers, further, air is ventilated via the space between the respective oil chambers to cool the lubricant oil therein.
In the above bearing device, the lubricant oil discharged from the both ends of the bearing is collected into the outer oil chambers which is plurarity of the oil chambers formed by dividing the oil tank, and the lubricant oil is moved downward in the respective oil chambers and thereafter is returned to an oil chamber wherein the oil ring disposed via the communicating tubes provided at the bottom of the respective oil chambers. Further, the lubricant oil is cooled by ventilating air passing via the space formed between the respective oil chambers.
In the conventional bearing device discussed above, the air mixing into the lubricant oil can not be avoided because the lubricant oil contacts with air during discharge thereof from the bearing lubricating surface and collection thereof into the oil tank, therefore the lubricant oil which has been discharged from the bearing lubricating surface and collected in the oil tank is heated to a high temperature, and possibly the oil is clouded into a milky color due to generation of air bubbles therein. However, there are no specific measures for removing the air bubbles mixed into the lubricant oil such that the lubricant oil is insufficiently cooled by natural heat radiation via the outer walls of the oil tank which results in unsatisfactory lubrication of the bearing.